This course teaches how to design, build, test, and operate secure software in modern development environments. It replaces bolt-on security approaches with secure-by-design practices embedded across the full system lifecycle, from architecture and development through deployment and operations. Learners explore how security integrates with DevOps and CI/CD pipelines, then apply secure design and threat modelling techniques to identify and manage risk early. The course develops practical understanding of security testing, vulnerability management, identity and access control, data security, and cryptography, forming a strong foundation for secure application development.Real-world weaknesses are examined using the latest OWASP Top 10, showing how vulnerabilities emerge and how they can be prevented through better design, coding, and configuration. Software supply chain risks, including third-party components and cloud-native dependencies, are also covered. The course extends into AI security, introducing the AI lifecycle, AI-specific threats, and the ETSI EN 304 233 global standard for securing large language models, agentic systems, data, and prompts. By the end of the course, learners can apply secure engineering practices to build resilient, trustworthy software and AI-enabled systems.